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Physics Chapter 6 Quiz
Terms in this set (38)
3 components by which sound attenuates:
A reduction of intensity in a sound beam to one-quarter of its original value is _______ dB
-6, or 1/4 (getting weaker)
Sound waves reflected in one direction from a smooth boundary
Diffuse reflection; backscatter:
Sound waves reflected in more than one direction from an irregular surface
When sound waves reflect in one direction it is:
Refraction occurs under what two conditions:
1. Oblique Incidence (not normal)
2. Different Prop. Speeds
Increased Frequency=Increased scattering=Increase attenuation, therefore:
Scattering is DIRECTLY related to frequency
What is P.O.R.N.N.
Two medias with the same densities, the propagation speed in one of the mediums is 10% higher than in the other medium, which medium has a higher impedance?
The medium with the higher prop. speed has a higher impedance. Propagation speed and impedance are DIRECTLY related.
density (kg/m3) x prop. speed (m/s) =
Impedance, reported in Z.
Transmission Intensity/Incident Intensity x 100 =
Intensity Transmission Coefficient
Reflection Coefficient + transmission coefficient = 100% =
Conservation of energy
Attenuation coefficient(dB/cm) x distance(cm)=
Reflected intensity + transmitted intensity =
sin(transmission angle)/sin(incident angle)= speed of Medium/speed of Medium 1 =
Snell's Law (pertains to refraction)
Reflection at a boundary between 2 soft tissue medias is what percent?
1% (or less)
Is a rate of attenuation per centimeter (dB/cm)
What percent is refracted in a boundary of normal incidence with identical impedances?
None, 0%; Refraction does not occur in identical prop. speeds
What attenuates greater than soft tissue?
Bone, lung and air.
Tissue and bone at a boundary of normal incidence have how much reflection?
3 dB does what to a wave's intensity?
Doubles it. 3 dB=2x bigger
100 mW/cm at -10dB equals what?
1/10th. The intensity is reduced 1/10 of its original value.
What percent of the wave is reflected when sound strikes soft tissue and bone?
What percent of the wave is reflected when sound strikes soft and air?
What attenuates less than soft tissue?
Fat, blood, urine, biologic fluids and water. (from low to lowest)
The 3 factors of Total Attenuation are:
1. The frequency of the sound
2. The distance the beam travels
3. The tissue through which the sound wave travels
Is frequency directly related to scattering and attenuation?
Yes. Higher frequency sound beams scatter more, weaken attenuation
As frequency goes down, what happens to the depth of penetration?
It increases. The deeper the depth of penetration, the lower frequency needed.
As the path length of a sound wave increases, what happens to the attenuation coefficient?
It remains the same.
When the sound beam strikes a boundary at any angle other than 90 degrees.
When the sound beam strikes the boundary at exactly 90 degrees.
the sound waves intensity immediately before it strikes a boundary.
Intensity Transmission Coefficient (ITC)
The percentage of intensity that passes in the forward direction when sound beams strike an interface between 2 media.
Attenuation Coefficient and Frequency in soft tissue are:
Directly related. Attenuation coefficient is one-half the frequency.
The half-value layer thickness depends on what 2 factors?
2. Frequency of sound
Half-Value layer thickness:
The distance sound travels in a tissue that reduces the intensity of sound to "one-half" its original value.
Two physical principles of reflection with oblique incidence:
1. Conservation of energy
2. Reflection angle=incident angle
Refraction can be defined as:
Transmission with a bend
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